Cell persistence transmitter



April 29, 1930. r c. F. JENKINS I CELL PERSIS TENCE TRANSMITTER Filed July 16, 1928 IEIEI nnmnnn HIHH Fatented Apr. 29, 1930 APR a rare animate UNITED STATES CHARLES FRANCIS JENKINS, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO JENKINS LABORATORIES, .OF WASHINGTON, DISTRICT RATION or THE DISTRICT or COLUMBIA OF COLUMBIA, A CORPO- cELL rEasrsTENcE TRANSMITTER Application filed July 16,

This invention relates to radiovision (Vision by radio) or television (vision by wire), and has for its principal object means whereby the current output of the photoelectric or lightsensitive cells employed is increased by several thousand times.

In all methods heretofore suggested the image of the scene to be transmitted is swept across a light-sensitive cell in successive lines; or, if a single object, may be swept by an 11- luminating spot of light. The light sensitive cell is excited by the light energy of each particular elementary area of the image plane only for a small fraction of a second. This is because of the limitation of the completion time for scanning of the Whole image, namely, persistence of vision of the human eye. This time may be as long as one-tenth of a second, though to avoid the flicker phenomena, the maximum time is usually not more than onefifteenth of a second.

But ifthe image area be assumed to be divided into 50 lines and each line into 50 divisions, each elementary area is but 1/2500 part of the Whole. That is, it is effected by its particular elementary light strength for but 1/2500 of 1/15 of a second, or 1/32500 part of a second.

This is well known, and accounts for the many schemes which have been proposed to conserve or increase the light-current output of the cells; for example, by employing very large cells, or by increasing the strength of the light falling on the cell.

Such methods give but a very small increase in cell output over old methods, and, therefore, radiovision and television transmission have been limited to simple objects and single subjects; and, even then only with indifferent results, for the light current efficiency is still limited to 1/2500 part of the ideal scheme, i. e., continuous elementary area activity.

The present invention employs just that very phenomena, namely, continuous elementary area cell activity, and, therefore, other conditions being equal, the cell-current output is two thousand, five hundred times greater.

In general, this new method differs ifrom 1928. Serial N'O. 292,992.

the old in that whereas the old method acti vated the cell' and immediately fed the resultant current into the transmitted circuit, or a time-current equal to 1/2500 of the-image time (1/15 of a second), the present method activates the cell all the time, accumulates the resultant current, and-discharges it into the transmitted circuit in the elementary time.

There are other advantages possible, however. For example,'instead of employing a light sensitive cell which has a reaction time of a millionth of a second, one may employ a cell having a reaction time of but 1/15 of a second. And as such cells usually have a light-current output efficiency many hundred times greater than the potassium cells heretofore employed, the possibilities in radiovision are little more limited than they are in film movies camera work. 4

With these and other objects in View, the

invention consists in the novel method and combination of means herein described and illustrated, and more particularly pointed out in the claims.

In the schematic drawings herewith, Fig-' ure 1 is a side elevation of the device; Figure 2 a partial view. of the light-sensitive image plane showing how the elementary areas are provided with individual cells; Figure ,3 det ails of cell-loading and discharge circuits.

In Figure 1, A is the subject to be transmitted; B a. lens for imaging the scene onto the cell-area plane C, which consists of aplurality of small light-sensitive cells D, D, D, from each of which a wire extends to a segment S, of the ommutator of the switching gear;,the support G for the cells D acting as a common return of the discharge circuit.

In Figure 3 the cells D are in a circuit with a battery E, and a condenser F.

The normal result of the action of the battery when light falls on the cell is to charge the condenser, which, of course, acts to accumulate a charge equal to its capacity. The amount of this cumulative charge oh the condenser is a factor of the light intensity on the coilisidered as a factor of the light strength on y.

The time referred to is 1/15 of a second, the time between discharges of the condenser, namely, from the moment the commutator brush of the switching gear G touches a segment S, and its return to the elementary area 7 represented thereby."

Assuming the cell D (Figure 3) to have been exposed to light, then circuit completed through C, E*, F S and the switching gear G and G and coupling coil R, back to D obviously discharges the condenser F After such discharge the commutator brush passes on to the next segment to discharge the next cell-battery-condenser circuit, while the previous condenser begins 'to accumulate a new charge proportionate to the light strength falling thereon at the moment.

It will appear obvious that as the total charge in the condenser is proportionate to the intensity of the light falling on the cell, the current discharged from the condensera-ccumulator may, at some distant place, be translated back into a corresponding strength of light. If this current light translation occurs at the right time to illuminate an elementary area corresponding to the light-cell area of the analyzed image at the transmitter, then an exact facsimile of the scene at the transmitting station will be reproduced at the receiving station.

Obviously, I do not wish to limit myself to any particular light-sensitive cell; nor to any definite number of elementary areas per image. In actual practice 2304. instead of 2500 elementary areas are preferred.

What I claim is 1. A plurality of light-current translating devices, an impulse storing element in circuit with each device, and means for connecting the storing elements into a common circuit.

2. A plurality of light-sensitive cells, an individual impulse storing element in circuit with each cell, and a commutator for connecting the storing elements into a common circuit.

3. In a light-current translating device, an image plane divided into electrically-separated elementary areas, a separate storing element in circuit with each area, and means for connecting said storing elements into a common circuit.

4. In a light-sensitive device, an image plane divided into individual light-sensitive elementary areas, an impulse storing element for each of said elementary areas, and adapted to be energized in accordance with the characteristics of the associated area, and means for connecting said storing element in succession to a common circuit.

5. The method of signaling which comprises energizing a light sensitive device 1n accordance with the characteristics of an elemental area of a visual representation, controlling a storing device in accordance with the resistance from said light sensitive device, and connecting said storing device to a transmission channel.

6. The method of signaling which comprises s'imultaneously energizing a plurality of separate light sensitive devices, each device corresponding to an elemental area of a visual representation, controlling storing devices in accordance with the operation of the associated light sensitive devices, and connecting the storing devices to a transmission channel.

7. The method according to claim 6, in which the storing devices are controlled simultaneously by the associated light sensitive devices and storing devices are connected successively to the transmission channel.

8. The method of transmitting a visual representation, which comprises translating the characteristics of the elemental areas of the representation into electrostatic charges, and applying said charges to a transmission channel.

9. The method of transmitting a visual representation which comprises simultaneously translating the characteristics of a plurality of elementary areas of the representation into corresponding electro-static charges, and successively connecting said charges to a common transmission channel.

10. In a system for transmitting visual representati ns, the combination of a plurality of light sensitive devices, means. for projecting on said devices an image of the representation to be transmitted, means for translating the responses of said device into corresponding electric charges, and means for applying said charges to a transmission channe 11. The method according to claim 10 in which the charges are connected to the transmission channel in succession.

12. In a system for transmitting visual representations, a plurality of light sensitive devices, means for projecting upon said devices an image of the representation to be transmitted, an electro-static storing device associated with each light sensitive device, a transmission channel, and means for successively connecting each of said storing devices to said channel.

13. A system according to claim 12 in which the means for connecting the storing device to the transmission channel includes a continuously operating commutator.

In testimony whereof I have ailixed my signature.

CHARLES FRANCIS JENKINS. 

